As with everything, individual thoughts by individual folks.
Sometimes bias sometimes ignorance. (Please understand the definition of this word)
My "individual" assessment of a good producer, is not only his off spring but the ability to produce afterwards.
Now you could breed some dog 100 times and keep looking at one and finally make W out of them but the law of Averages are still there.
Now if you have a dog for one reason or another that was need to a limited amount of dogs and those dogs themselves are not worth the sperm you wasted how can you blame the stud.
There have been many dogs locally (North America) that were bred very free times and in one litter gave you a couple of Ch. and multiple winners then you know you have a good producer.
If I'm not mistaken I don't think Redboy was need to anything but his offspring, offspring or half brother/sister ..more or less, yet he produced pretty well I would say.
Now Friscowas bred more times than you can say. Thank You. So does that make him a great producer ?
I can tell you from the dogs I have seen go. Example,. Buck. Gr. Ch tornado.would not hesitate to breed to them get a dig off off them.